SUMMER will be “knocked on the head” when tropical storm Bertha hits Britain this weekend.

The swirling cyclone hurtling across the Atlantic is expected to reach the UK on Sunday.

It will unleash violent gales and torrential downpours, triggering weeks of miserable weather.

Forecasters have predicted that almost a month’s worth of rain could fall in a matter of hours.

They said Bertha, which has moved from a hurricane to a tropical storm, threatens to knock the jet stream out of position, affecting Britain’s weather for weeks.

It means we could face at least a fortnight of wind and rain, making it feel like autumn has arrived early.

The jet stream is usually in a northerly position at this time of year allowing high pressure and warm air to flow in from the south.

Forecasters said a shift southwards would lead to a much wetter and windier picture. Jim Dale, forecaster for British Weather Services, said that the UK faces 70mph gales on Sunday with heavy showers dumping more than an inch of rain in hours.

He warned winds will be strong enough to cause “some weather damage” across the country.

This system is still showing signs of ripping right across the country and it has the potential to do some damage. We could see up to 60mm of rain fall in a short time, and because of the violent nature of this system it could pack a punch and cause a bit

Jonathan Powell, Vantage Weather Services

“Bertha looks like moving slightly further south with the low now expected to go right across the middle of the country with Sunday the main day,” he said. “The thing with this is it is going to catch people off guard.

The worst-case scenario is we could be looking at 70mph winds and up to 1kins of rain. It may also pull the jet stream further south making it much more unsettled and knocking summer on the head.High summer is definitely going to be put on hold, this is going to be a shock to the system. We don’t see any sign of a return to high summer for the best part of August.”

It comes as parts of the UK were hit by more than an inch of rain in a matter of hours overnight on Tuesday. The Met office said nearly 1fins fell in Wales with up to an inch in London.

Jonathan Powell, forecaster for Vantage Weather Services, said almost 2dins of rain – almost a month’s worth – could fall on Sunday.

He said a separate low-pressure system heading towards the UK tomorrow will make things feel warm and muggy before the weekend storm sends temperatures plunging.

He said: “It is going to be a very chaotic mix from the end of the week.

“This system is still showing signs of ripping right across the country and it has the potential to do some damage. We could see up to 60mm (more than 2kins) of rain fall in a short time, and because of the violent nature of this system it could pack a punch and cause a bit of disruption.

Bertha is set to unleash weeks of terrible weather with gales and torrential rain expected [GETTY]

“It follows another low pressure before the weekend which could push temperatures to 86F (30C), but then afterwards it will be much cooler. It is a very chaotic picture.”

The Met Office last night said Bertha’s intensity and track is “changing all the time”.

It issued a severe weather warning for rain tomorrow with two inches likely in a matter of hours.

A statement read: “A deepening area of low pressure is likely to pass close to south-eastern England on Friday. With very warm, humid air over the region there is the potential for the rain to become very heavy during the afternoon with totals of more than 50mm (2ins) locally.’

Spokeswoman Laura Young said most places can expect rain and it will be a windy and miserable weekend.

She said: “We will be assessing the situation with regard to warnings.”

Netweather forecaster Nick Finnis said: “With Atlantic weather fronts pushing cloud and rain in across western Scotland and Northern Ireland and there is a risk of persistent and heavy rain moving up across parts of southern and eastern England too.”

Weatheronline forecaster Simon Keeling said: “It’s an unsettled weekend and week ahead as the remnants of hurricane Bertha make their presence felt. There is a risk of severe gales this weekend, especially in the West.”